The mammalian uterus is a unique immunologic organ in its conflicting capabilities. It can recognize and respond to antigens presented within its confines and yet the uterus serves as a natural graft site for the developing allogeneic fetus. The proposed research will use nonpregnant animals, eliminating many of the factors which complicate the immune responses during pregnancy, to study immunologic functions in the female rat after interauterine presentation of antigen. The work described will explore the means of antigen processing from within the uterine lumen, the localization of this antigen and the cells with which it interacts, and the eventual fate of these sensitized cells. One goal of the study proposed is to determine whether the uterus is a part of the common mucosal immune system (which includes the gut, respiratory tract, mammary tissues, etc.) or if it is an independent organ system with the putative capacity for secretory immune responses. Demonstration of the uterus' ability to produce IgA, either in the uterine tissue itself, in the lymph nodes draining the uterus, and/or in all sites of the mucosal immune system will clarify the contribution of the uterus to the host's overall secretory immunity. This, in turn, will help to understand the role that uterine immunity may play in protection of the female from exogenous agents. Cell trafficking studies will illustrate how-and if-the responses induced after uterine immunization remain localized in lymph nodes draining the uterus. Investigating the mechanisms of the immune functions which develop after presentation of antigen in the uterus can further our understanding of the uterus' dual role as a site of effective immunization of the female and as an almost inviolable site for attachment and successful maintenance of a fetal allograft.